Generally, the filling of receptacles with solid particles (granular solids) is accomplished by transfer of the solid by means of a hopper and/or a cone either manually or mechanically or by pneumatic transference.
As a general rule, it is of the utmost interest to introduce the maximum of products into a given space, as much in order to reduce the cost of storage as for other specific reasons such as, for example, to standardise storage or reduce the volume of air or gas in the container.
Everyday storage situations relate to cereals (in silos), food products intended for consumption or for livestock, agro-alimentary products, fertilisers, chemicals, granulated plastics, pharmaceutical and/or cosmetic products and any other divided solid material (grains or tablets or extruded granulate material, pills, agglomerates, crushed materials etc.). Their other field of application consists of receptacles or chemical reactors intended to be filled with solid particles such as: catalysts, absorbents, reagents, packings, sundry fillings and the like . . .
In this case, it is almost always advantageous to place the maximum of solid product inside the reactor in order to enhance the activity thereof per unit volume and therefore the efficiency and effective service life (cycle time or working life) thanks to the ability to space out the periods of plant stoppage. It is likewise important to avoid subsequent shrinkage of the divided solid, which always occurs in an inhomogeneous fashion, encouraging undesirable and preferred passages of fluid in the case of a chemical reactor.
The use of a dispersion head placed under the hopper and consisting of plates, preferably three or four plates, and fixed on a shaft driven by a motor rigid with the hopper is a known method. For example, the patent GB 2 168 330 relates to the use of a single plate provided with arcuate segments of different radii; the patent DE 2 703 329 has three discs of different diameters which rotate thanks to an endless groove which provides for feeding to the hopper; similarly, U.S. Pat. No. 4,433,707 comprises three discs of decreasing radii, the largest being that which is closest to the hopper.
The patent applications of the Applicants (FR 89/05.780 and the additions FR 89/10.287 and FR 89/13.469) also relate to the use of at least three plates of different radii but the innovation lies in a preferred form of these plates, spiralling, such that the spiral is continuous when one changes from one plate to the next.
Many other methods are also used all of which ensure a more or less homogeneous filling of the receptacles, silos or reactors.
Despite everything, the use of any one of the aforementioned methods does not make it possible homogeneously and completely to fill the various configurations of receptacles.
For example, filling small diameter receptacles remains very difficult to achieve; indeed, in cases where the rotary speed of the shaft is not very great, the bottom plate(s) cannot impart sufficient linear velocity to the particles which are spread on them for the latter to fall into the receptacle and then the plate(s) will become blocked. When the speed diminishes and reaches a sufficiently low level, the bottom plate is the first to become blocked and then the plate which is immediately above it and so on as the speed continues to drop. Therefore, filling is no longer regular and a depression forms in the center of the bed of particles inside the receptacle.
Accordingly, there is a minimum speed of rotation for a given rate of flow. Below this speed, the rate of flow is reduced in order to avoid the lower plates from becoming clogged.
This problem of the clogging of at least one lower plates also arises when filling of the receptacle is commenced.
Furthermore, as a general case, it is not possible to conform to the desirable rate of flow of filling. For example, if it is too high, the rotary speed of the shaft may need to be increased. Consequently, the distribution of particles within the body of the receptacle will be altered and there will be more particles at the periphery than in the center.
On the one hand, one and the same apparatus (based on one of the methods) does not make it possible to fill receptacles of different diameters without the dispersion head being changed.